This combination of three photos shows, from left, Los Angeles Mayor Antonio Villaraigosa, Attorney General Jerry Brown and San Francisco Mayor Gavin Newsom. Handsome, charismatic and politically bold, Gavin Newsom and his Southern California counterpart, Antonio Villaraigosa, are naturals to take over California's Democratic Party for the next generation. There's just one obstacle, and he's a formidable one: Former two-term governor Jerry Brown. (AP Photo)

Photo: AP

This combination of three photos shows, from left, Los Angeles...

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20MAR03-FD-HO --- Ken Starr

Photo: Handout, The Chronicle

20MAR03-FD-HO --- Ken Starr

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Attorney General Jerry Brown discusses how his office will handle the passage of Proposition 8 during a news conference in Sacramento, Calif., Wednesday, Nov. 5, 2008. Approved by voters in Tuesday's election, Prop. 8 will change California's Constitution to ban same-sex marriage.

State Attorney General Jerry Brown, in a surprise turnabout, asked the California Supreme Court on Friday to overturn Proposition 8, saying the voter-approved ban on same-sex marriage violates basic rights guaranteed in the state Constitution.

Brown, who is required to defend state laws unless he cannot find reasonable legal grounds to do so, said after Prop. 8 passed Nov. 4 that he would support the initiative before the state's high court.

But in a lengthy filing late Friday, he argued that the constitutional amendment was "inconsistent with the guarantees of individual liberty" in California's governing charter.

"Proposition 8 must be invalidated because the amendment process cannot be used to extinguish fundamental constitutional rights without compelling justification," Brown said.

The authors of the state Constitution, he said, did not intend "to put a group's right to enjoy liberty to a popular vote."

Hours earlier, sponsors of Prop. 8 filed arguments asking the court to uphold the ballot measure, which passed with a 52 percent majority. Andrew Pugno, attorney for the Yes on 8 campaign, said he was disappointed by Brown's stance.

"It's unfortunate that the attorney general would not do his duty to defend the will of the voters," Pugno said.

The position of the attorney general, the state's top lawyer, ordinarily carries considerable weight with the court. Brown's office was on the losing side, however, when the court overturned California's previous ban on same-sex marriage in May.

Asked about his change of position, Brown said Friday evening that since his initial comments the day after the election, he and senior lawyers in his office had looked closely at the court's precedents and at the recent marriage ruling and concluded they couldn't defend Prop. 8.

"We have a conflict between the amendment power (through voter initiatives) and the duty of the Supreme Court to protect minorities and safeguard liberty," Brown said.

Fundamental rights in the state Constitution, including the right to marry that the state's high court has recognized, "become a dead letter if they can just be amended" by popular vote, Brown said.

The Yes on 8 forces' brief was filed by Kenneth Starr, the former Whitewater special prosecutor and now dean of Pepperdine University law school. He argued that the court should preserve the people's lawmaking powers by upholding the initiative and invalidating 18,000 same-sex weddings performed before the election.

Prop. 8 "does not broadly seek to diminish or eliminate the constitutional or civil rights of gays and lesbians," but is simply "about restoring and maintaining the traditional definition of marriage," Starr said. Decades of legal precedents, he said, require "judges - as servants of the people - to bow to the will of those whom they serve."

The court ruled 4-3 on May 15 that California's ban on same-sex marriage violated the constitutional rights of gays and lesbians to marry the partner of their choice and discriminated on the basis of sexual orientation. Prop. 8 amended the state Constitution to overturn the ruling and declare that only marriage between a man and a woman is "valid or recognized in California."

The court is reviewing lawsuits filed by gay and lesbian couples and by an array of local governments, led by San Francisco, that contend the ballot measure exceeded the legal limits on initiatives by destroying fundamental rights and stripping judges of their authority to protect a historically persecuted minority.

Such profound changes, the plaintiffs argue, amount to a constitutional revision - not merely an amendment - and require a two-thirds vote of the Legislature to reach the ballot.

The justices could hear the cases as early as March and would be required to rule within 90 days. Other interested parties on both sides are scheduled to submit written arguments Jan. 15.

Starr argued Friday that Prop. 8 is a relatively modest measure and not the type of far-reaching change that qualifies as a constitutional revision.

"It simply reinstates the traditional definition of marriage without any impact on the foundational powers of government," he wrote. Judges, Starr said, retain their power to interpret the law and have never held a "mandate to protect minority rights or ensure equality apart from the law."

He also said Prop. 8's language, declaring that only marriages between men and women are "valid or recognized," invalidates all same-sex marriages conducted in California and bars the state from acknowledging those performed elsewhere. That intention was underscored by Yes on 8 ballot arguments declaring that only opposite-sex marriages would be recognized in the state "regardless of when or where performed," Starr said.

Brown disagreed on that issue as well, saying in his brief that Prop. 8 did not explicitly state it would apply retroactively. If upheld, he said, the measure should be interpreted to apply only to marriages performed since it passed.

The attorney general agreed with Starr that the ballot measure is not a constitutional revision and does not weaken judicial powers. But Brown said Prop. 8 conflicts with the Declaration of Rights, the basic guarantees of liberty declared in the first sentences of California's Constitution.

As the "chief law officer of the state," Brown said in his brief, he is "duty bound to uphold the whole of the Constitution" and not merely the power of the people to change the laws by initiative.